1. Field of the Invention
The present invention relates to a plate fin and tube heat exchanger used in air conditioning, refrigeration and other applications.
2. Description of the Related Art
Plate fin and tube heat exchangers are used in a wide variety of applications in which it is desired to exchange heat between two fluids, a refrigerant flowing in the heat exchanger tubes and, typically, air flowing around the heat exchanger plate fins and tube exteriors.
In such a heat exchanger, a plurality of plate fins having holes are arranged parallel to each other. Heat exchanger tubes pass through the holes in the plate fins. The heat exchanger tubes are expanded in the radial direction to tightly connect them with the plate fins. A tight connection between the tubes and the plate fins increases the heat transfer performance. A conventional heat exchanger has heat exchanger tubes arranged in one row in the longitudinal direction of the plate fins. In the conventional heat exchanger, as the number of heat exchanger tubes increases, more heat is transferred between a fluid passing through the tubes and the fins. However, the air volume passing through the heat exchanger decreases because the gaps or distances between the adjacent heat exchanger tubes become narrow. As a result, the total heat transfer performance is not greatly improved.
In order to improve the heat transfer performance, a heat exchanger having a plurality of staggered rows of tubes through the plate fins was developed as described in U.S. Pat. No. 4,434,843. The heat exchanger uses a large number of tubes provided in a zigzag or staggered configuration along the plate fins. The gaps between adjacent tubes are sufficient to ensure a large air volume passing therethrough so that the heat transfer performance is improved.
There is also known a bent type heat exchanger which is partially bent in the longitudinal direction of the heat exchanger tubes. The bent type heat exchanger, which is formed with a corner section and straight section, reduces the size of the heat exchanger unit. However, it is not simple to apply the above described staggered heat exchanger in the bent type heat exchanger, because the length of the inner row of bent tubes must be shorter than that of the outer row of bent tubes.